1. Magma is a mixture of melted rock and hot gasses.

2. Not all magma is the same: 1. the kind of melted rock; and 2. the amount of gas in the magma; make different types of magma.

3. The amount of silica (quartz crystals) in the rock from which magma is made effects the viscosity or thickness.

4. More silica (quartz) in the magma makes it thicker or higher viscosity.

5. BASALTIC – made from oceanic crust and mantle material, so it has low silica content.

6. Low silica content means low viscosity, thinner magma.

7. BASALTIC – made from oceanic crust and mantle material, so it has low silica content. Low silica content means low viscosity, thinner magma. Makes quiet volcanoes, like Hawaiian Islands, Iceland, Africa.

8. GRANITIC – made from continental crust, so it has high silica content.

9. High silica content means high viscosity, thicker magma.

10. GRANITIC – made from continental crust, so it has high silica content. High silica content means high viscosity, thicker magma. Makes explosive volcanoes, like Mt. St. Helens, Vesuvius, Krakatau.

11. The amount of water in the rock also determines whether a volcano is quiet or explosive.

12. More water in the rock makes it easier to melt.

13. The amount of water in the rock also determines whether a volcano is quiet or explosive. More water in the rock makes it easier to melt. The water also turns to water vapor, which builds up as gas bubbles.

14. MORE WATER, MORE GAS, BIGGER BLAST!

15. How would you get more water in the rock?

16. MORE WATER, MORE GAS, BIGGER BLAST! How would you get more water in the rock? In subduction zones, ocean water is also pulled down into the mantle with the plates.

17. Most volcanoes are found at convergent plate boundaries. WHY?

18. Most volcanoes are found at convergent plate boundaries. WHY? Subduction pushes oceanic crust into the mantle.

19. Most volcanoes are found at convergent plate boundaries. WHY? Subduction pushes oceanic crust into the mantle. The crust melts and rises back up to make volcanoes.

20. Volcanoes can also be found at divergent boundaries. Plates spread apart and lava oozes out.

22. HOT SPOTS – extra hot plume of hot mantle material rises up from the core and melts the crust. Examples: Hawaii, Yellowstone

25. MAGMA CHAMBER – pocket where magma collects.

26. VENT - opening in Earth’s crust where magma comes out.

27. MAGMA CHAMBER – pocket where magma collects. VENT - opening in Earth’s crust where magma comes out. CRATER – bowl shaped pit around the main vent.

28. MAGMA CHAMBER – pocket where magma collects. VENT - opening in Earth’s crust where magma comes out. CRATER – bowl shaped pit around the main vent. CALDERA – huge depression created when the magma chamber collapses.

31. SHIELD VOLCANO: volcano with broad, gently sloping sides.

32. Quiet eruptions, basaltic lava, little gas.

33. SHIELD VOLCANO: volcano with broad, gently sloping sides. Quiet eruptions, basaltic lava, little gas. Largest volcanoes – found at hotspots (Hawaii, Galapagos) and divergent boundaries (Iceland, East Africa).

35. COMPOSITE VOLCANO: A volcano with steep sides formed by layers of thick lava, tephra (hot rocks), and ash.

36. Usually have explosive eruptions, lots of gas, pyroclastic flows.

37. COMPOSITE VOLCANO: A volcano with steep sides formed by layers of thick lava, tephra (hot rocks), and ash. Usually have explosive eruptions, lots of gas, pyroclastic flows. Found at convergent boundaries with subduction zones – Mt. St. Helens, Krakatoa, Mt. Fuji, Mt. Rainier, Vesuvius.

39. CINDER CONE: small volcano with steep sides formed by tephra (hot rocks).

40. Large volcanoes usually have small cinder cones on them, like pimples.

42. A supervolcano is a volcano which is a thousand times bigger than any we have seen during recorded human history.

43. Geologic evidence shows that many such eruptions have happened in Earth’s past, and will likely happen again.

44. A supervolcano is a volcano which is a thousand times bigger than any we have seen during recorded human history. Geologic evidence shows that many such eruptions have happened in Earth’s past, and will likely happen again. These large eruptions can alter weather and climate and lead to extinction of species.

48. At least two supervolcanoes are suspected of creating or causing mass extinctions:

49. SIBERIAN TRAPS – 250 million years ago. May have caused Permian extinction.

50. At least two supervolcanoes are suspected of creating or causing mass extinctions: SIBERIAN TRAPS – 250 million years ago. May have caused Permian extinction. DECCAN TRAPS – 65 million years ago. Now suspected of killing off the dinosaurs.

51. Last erupted about 74,000 years ago.

52. 1,000 times bigger than Mt. St. Helens.

53. Last erupted about 74,000 years ago. 1,000 times bigger than Mt. St. Helens. Caldera is 100 kilometers long and 30 kilometers wide.

54. Last erupted about 74,000 years ago. 1,000 times bigger than Mt. St. Helens. Caldera is 100 kilometers long and 30 kilometers wide. Eruption created “volcanic winter” – ash and dust blown into the atmosphere blocks out the Sun.

56. “Volcanic winter” kills plants, makes the Earth colder. 60% of the human population may have died as a result of this eruption.

57. “Volcanic winter” kills plants, makes the Earth colder. 60% of the human population may have died as a result of this eruption.

58. Last erupted 640,000 years ago.

59. Smaller than Lake Toba, caldera is 72 km long and 55 km wide.

61. Last erupted 640,000 years ago. Smaller than Lake Toba, caldera is 72 km long and 55 km wide. Caused by North American plate moving across a “hot spot” in Earth’s mantle.

63. Last erupted 640,000 years ago. Smaller than Lake Toba, caldera is 72 km long and 55 km wide. Caused by North American plate moving across a “hot spot” in Earth’s mantle. Supereruptions on this hot spot have regularly occurred every 600,000 to 800,000 years.

64. In recent years, Yellowstone has seen increases in earthquakes around the caldera.

65. Ground has begun rising an average of 3 inches per year.

66. In recent years, Yellowstone has seen increases in earthquakes around the caldera. Ground has begun rising an average of 3 inches per year. Is it getting ready to erupt?

67. Supereruption would send 1000 cubic kilometers of ash into the air.

68. Ash would cover most the United States.

69. Supereruption would send 1000 cubic kilometers of ash into the air. Ash would cover most the United States. Ash could be as much as 6 inches deep in the Salt Lake Valley.

70. Supereruption would send 1000 cubic kilometers of ash into the air. Ash would cover most the United States. Ash could be as much as 6 inches deep in the Salt Lake Valley. Volcanic winter would effect climate in Utah and around the world.